A 3-month-old boy in respiratory distress presents to the emergency department. It is January, so you suspect the coarse wheezes heard on chest auscultation by the triage nurse are the result of a viral respiratory infection; you approve the administration of aerosolized albuterol. About 20 minutes later you are able to obtain from the mother a more complete history. She tells you the baby began having intermittent wheezing approximately 4 weeks ago and the episodes have become progressively worse. You then listen to the infant and discover that, in addition to wheezes, a holosystolic murmur can be heard along the left sternal border. The oxygen saturation obtained at triage was normal.
What is the most likely diagnosis?
What is the treatment for this condition?
ANSWERS TO CASE 24: Ventricular Septal Defect
Summary: A 3-month-old infant presents with respiratory distress, wheezing, and a soft holosystolic heart murmur. His symptoms began 4 weeks ago and have become progressively worse.
• Most likely diagnosis: Ventricular septal defect (VSD).
• Treatment: Medical management, and possible eventual surgical closure.
1. Recognize the presenting signs and symptoms of VSD.
2. Know the major acyanotic congenital heart lesions.
3. Be familiar with the fetal circulation (Figure 24-1).
Figure 24-1. Fetal circulation. (Reproduced, with permission, from Cunningham G, Leveno KL, Bloom SL. Williams Obstetrics. 22nd ed. New York, NY: McGraw-Hill; 2005.)
An acyanotic heart lesion is suspected in this child who has a new heart murmur without cyanosis. The fall in pulmonary vascular resistance that occurs in the weeks following birth allows blood to flow from left to right across a VSD, resulting in an audible murmur by 2 to 6 months of life. This child’s VSD is of sufficient size to result in congestive heart failure. Unlike the cause of wheezing in most of the other infants presenting to the emergency department in winter, this child’s respiratory distress is not due to a viral respiratory infection.
Acyanotic Heart Lesions
EISENMENGER SYNDROME:Pulmonary hypertension (HTN) resulting in right-to-left shunting of blood. This may occur with large ventricular septal defects (VSDs), atrioventricular canal lesions, and patent ductus arteriosus (PDA).
LEFT-TO-RIGHT SHUNT: Flow of blood from the systemic circulation into the pulmonary circulation across an anomalous connection, such as a PDA. Such lesions result in pulmonary congestion, but they typically do not cause cyanosis. Systemic hypoperfusion may result if the cause is an obstructive lesion (such as pulmonic or aortic valve stenosis, coarctation of the aorta).
WIDENED PULSE PRESSURE: An increase in the difference between systolic and diastolic pressures, resulting in a bounding arterial pulse. Many conditions may cause this finding, including fever, hyperthyroidism, anemia, arteriovenous fistulas, and PDA.
Congenital cardiac defects are first categorized according to the presence of cyanosis. They are then further classified according to chest radiograph findings of increased, normal, or decreased pulmonary vascular markings, and then finally according to ventricular forces indicated on electrocardiography. The majority of acyanotic lesions result in a change in volume load, usually from the systemic circulation to the pulmonary circulation (so called left-to-right shunt). Left untreated, defects that affect volume load can eventually result in increased pulmonary vascular pressure, causing reversal of blood flow across the defect and clinical cyanosis. Other forms of acyanotic defects cause changes in pressure; this group includes pulmonic and aortic valve stenosis and coarctation of the aorta.
Ventricular septal defect is the most common heart lesion in children, affecting 3 to 6 of every 1000 live term births (Figure 24-2). The majority of VSDs occur in the membranous portion of the septum, and small VSDs with minimal left-to-right shunts are the most common. Children with small VSDs usually are asymptomatic, and a harsh, left lower sternal border holosystolic murmur is detected on physical examination. The murmur of a large VSD may be less harsh because of the absence of a significant pressure gradient across the defect. Large lesions are accompanied by dyspnea, feeding difficulties, growth failure, and profuse perspiration, and they may lead to recurrent infections and cardiac failure. Infants with large VSDs generally are not cyanotic, but they may become dusky during feeding or crying. A VSD may not be detected in the first few weeks of life because of high right-sided pressures but become audible as pulmonary vascular resistance drops and left-to-right shunting of blood increases across the defect. In children with significant VSDs, chest radiography shows cardiomegaly and pulmonary vascular congestion, and the electrocardiogram (ECG) shows biventricular hypertrophy.
Figure 24-2. Image A shows the structure and blood flow inside a normal heart. Image B shows two common locations for a ventricular septal defect. The defect allows oxygen-rich blood from the left ventricle to mix with oxygen-poor blood in the right ventricle. (From the National Institutes of Health. http://www.nhlbi.nih.gov/health/health-topics/topics/chd/types.html [accessed 09/07/11].)
Most small VSDs close spontaneously by 6 to 12 months of life, especially if they occur in the muscular septum. Medical management is reserved for infants who are symptomatic from larger VSDs. Medications include diuretics (eg, furosemide, chlorothiazide) and afterload reduction agents (eg, an angiotensin-converting enzyme inhibitor) and sometimes digoxin. Affected infants also need adequate caloric intake, usually 140 kcal/kg/d, and may require feeding by nasogastric or gastrostomy tubes. When monitoring children with large VSDs, one should not be misled by a softening murmur, as this may herald pulmonary vascular disease or infundibular stenosis rather than closure of the defect.
Most children with large VSDs develop pulmonary vascular resistance after 1 year of age, although it can occur early; children with trisomy 21 are at particular risk of early disease. Children with persistently large shunts after 1 year of age usually undergo surgical closure, as one-third of these children have irreversible pulmonary vascular disease by 2 years of age (Eisenmenger syndrome).
Other acyanotic congenital heart lesions include PDA, atrial septal defects (ASDs), and atrioventricular septal defects. Patent ductus arteriosus is most commonly seen in preterm infants, but it also occurs in term infants. In utero, the ductus arteriosus shunts blood from the quiescent lungs through the pulmonary artery to the descending aorta. Shortly after birth, pulmonary resistance begins to fall, and vasoconstriction of the ductus occurs. Ductus closure in term infants usually occurs within 10 to 15 hours of birth and almost always by 2 days. Closure is delayed in premature infants, perhaps as a result of impaired vasoconstrictor response to increased oxygen tension. Failure of the ductus to close allows shunting of blood from the systemic circulation to the pulmonary circulation, with resultant myocardial stress, pulmonary vascular congestion, and respiratory difficulty. A small PDA usually results in no symptoms but is still closed medically (usually with indomethacin) or surgically (if medical therapy fails or is contraindicated) due to risk of infective endarteritis and paradoxical emboli. An infant with a large PDA typically has a systolic or continuous “machinerylike” heart murmur,an active precordium, and a widened pulse pressure. Closure is accomplished to treat heart failure and prevent Eisenmenger syndrome. Occasionally, a PDA is present in association with another congenital cardiac lesion and may be difficult to detect. For patients with coarctation or interruption of the aortic arch, a PDA is vital to maintaining blood flow to the systemic circulation. Likewise, a PDA in the presence of an obstructed pulmonic valve is essential for providing blood flow to the lungs (Figure 24-3). Such lesions are called ductus dependent, and the PDA patency is maintained with an infusion of prostaglandin E.
Figure 24-3. Angiography of persistent patent ductus arteriosus (PDA). AO, aorta; PA, pulmonary artery. (Reproduced, with permission, from Rudolph CD, Rudolph AM, Hostetter MK, Lister G, Siegel NJ, eds. Rudolph’s Pediatrics. 21st ed. New York, NY: McGraw-Hill; 2003:1819.)
Children with ASDs often are asymptomatic and the lesion discovered inadvertently on routine physical examination. Large defects may cause mild growth failure and exercise intolerance not appreciated except in retrospect after defect closure. Physical findings include a widely split second heart sound that does not vary with respiration (“fixed splitting”), and a systolic murmur at the left upper and midsternal borders caused by high-volume blood flow from the right ventricle into the normal pulmonary artery; the murmur is not blood flowing across the ASD itself. A lower left sternal border diastolic murmur produced by increased flow across the tricuspid valve may be present. The chest radiograph reveals an enlarged right atrium, right ventricle, and pulmonary artery and increased pulmonary vascularity; ECG shows right ventricular hypertrophy and sometimes right-axis deviation. Atrial septal defects are well tolerated during childhood but can lead to pulmonary HTN in adulthood or atrial arrhythmias from atrial enlargement. Infective endocarditis is rare; routine prophylaxis is not recommended. An isolated patent foramen ovale usually is not clinically significant and is not considered an ASD.
Atrioventricular septal defect (also known as AV canal or endocardial cushion defect) consists of a contiguous atrial and ventricular septal defect as well as abnormal AV (ie, mitral and tricuspid) valves. This acyanotic lesion requires correction in infancy to prevent cardiac failure and associated complications. A systolic murmur of large pulmonary flow is present, and a lower left sternal border diastolic murmur is heard. The second heart sound may be widely split. The chest radiograph and ECG show cardiac enlargement; pulmonary vascularity is increased on the chest film.
Left untreated, these children develop cardiac failure, growth failure, and recurrent pulmonary infections in infancy. Pulmonary HTN develops with eventual right-to-left shunting and cyanosis. Surgical correction is performed in infancy.
24.1 A 2-month-old girl with Down syndrome is noted to have a systolic and a diastolic heart murmur, and the second heart sound is split. The liver edge is palpable 4 cm below the right costal margin. Her mother reports that lately the baby has been sweaty and sometimes blue around the mouth when she nurses, and she seems to be eating less than previously. Her electrocardiogram (ECG) shows a superiorly oriented QRS frontal plane axis with counterclockwise depolarization pattern and right ventricular hypertrophy. Which of the following is the most likely diagnosis?
A. Atrial septal defect
B. Atrioventricular canal defect
C. Patent ductus arteriosus
D. Patent foramen ovale
E. Ventricular septal defect
24.2 A 1000-g boy, delivered at 29 weeks’ gestation, is admitted to the neonatal intensive care unit, where he receives routine care. He does well until day 5 of life, when he develops an increased respiratory rate, mild subcostal retractions, and a widened pulse pressure, but no cyanosis or increased oxygen requirement. A continuous murmur is heard along the left sternal border. Chest radiography shows pulmonary vascular congestion. Which of the following medications may best relieve his symptoms?
B. Racemic epinephrine
24.3 A 12-month-old boy with a stable but moderate-size ventricular septal defect presents to the pediatric dentist for cleaning and management of his multiple caries. Prior to the procedure, he should receive which of the following?
E. None of the above
24.4 A previously healthy term infant suddenly develops respiratory distress on day 3 of life. An echocardiogram reveals coarctation of the aorta. Which of the following is the most appropriate treatment for immediate stabilization of this infant?
D. Racemic epinephrine
E. Prostaglandin therapy
24.1 B. Atrioventricular canal defect is common among children with Down syndrome. This infant’s symptoms and clinical findings are most consistent with this diagnosis. While a simple VSD is common in patients with Down syndrome, the multitude of heart murmurs and ECG findings make this answer less likely.
24.2 C. A noncyanotic heart lesion is suspected in this child who has a new heart murmur without a corresponding increase in oxygen requirements. The murmur, not heard at birth, becomes evident after the pulmonary vascular resistance falls. His age, history, and physical findings are consistent with a patent ductus arteriosus (PDA). Indomethacin or surgical closure is used to treat this condition.
24.3 E. The guidelines for the use of prophylactic antibiotics are updated frequently by the American Heart Association. Among those currently recommended to receive antibiotic prophylactic treatment are patients for whom any heart infection would result in the highest incidence of adverse outcome: previous history of endocarditis, prosthetic valve or material for repair, heart transplant patients, and severe or partially repaired cyanotic congenital heart defects.
24.4 E. This infant’s symptoms started when his ductus arteriosus began to close. Prostaglandin therapy can reverse this process in the short-term. Surgery or catheterization techniques provide definitive repair.
Acyanotic heart lesions are characterized by shunting of blood from the systemic circulation to the pulmonary circulation (“left-to-right shunt”).
The most common congenital acyanotic heart lesion is the ventricular septal defect. Patent ductus arteriosus, atrial septal defect, and arteriovenous canal are other left-to-right shunt lesions.
Left-to-right shunts eventually can reverse direction (right-to-left) and cause cyanosis if pulmonary hypertension develops (Eisenmenger syndrome).
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